1. Field
The following description relates to an X-ray imaging apparatus and a method of generating an X-ray image.
2. Description of the Related Art
X-ray imaging apparatuses are devices that irradiate an object, for example, a human body, with X-rays having a predetermine energy band, detects X-rays that have passed through the object, and acquires an image from the X-rays. Accordingly, an X-ray image of the inside of the object, for example, internal parts of the human body, may be acquired. X-ray imaging has been widely applied to various fields, such as, for example, medical diagnosis and baggage screening because it is possible to nondestructively inspect the internal structure of an object.
The X-ray imaging apparatus may obtain the internal structure of an object based on difference in X-ray absorbance of internal parts of the object. When an object is irradiated with X-rays, tissues having a higher X-ray absorbance among the internal tissues absorb most of the X-rays, and tissues having a lower X-ray absorbance transmit most of the X-rays. An X-ray detector detects the transmitted X-rays, and an X-ray image is generated according to the detected X-rays, thereby detecting the internal tissues of the object.
Types of detectable tissues vary according to the energy band of the emitted X-rays. For example, hard tissues such as bones may be detected when an object, for example, a human body, is irradiated with high energy band X-rays. On the other hand, when the object is irradiated with low energy band X-rays, transmittance of the X-rays through the internal tissues of the object decreases, thereby enabling detection of soft tissues. Thus, full field digital mammography (FFDM) may detect abnormalities of a breast by irradiating the breast with low energy band X-rays.
A multi-energy X-ray (MEX) image is an X-ray image used to inspect and confirm various tissues inside an object by taking images of the object plural times using X-rays having various energy bands. In order to obtain the multi-energy X-ray image, a method of exposing the object sequentially to X-rays having different energy bands has been used and X-ray photons may be detected through charge integration. However, this method exposes the object to X-rays plural times.
Alternatively, the multi-energy X-ray image may be acquired by converting single X-ray photons into electrical signals using a photon counting detector and attenuating amplitudes of the electrical signals by use of proportional relationship between the amplitudes of the converted electrical signals and energy. In the latter case, the multi-energy X-ray image may be acquired by use of a single stage of X-ray irradiation. However, this method has not been commercialized due to difficulties in the manufacturing process.